Not Applicable
Not Applicable
This invention relates to a process for the preparation of mixed ethoxylated alkylphenol/ethoxy sulfate surfactant systems, to the surfactants thus produced, and to synthetic detergent formulations incorporating the same. In particular, it relates to the preparation of ethoxylated alkylphenol/sulfated ethoxylated alkylphenol surfactant blends providing low cost, low capital, low-energy intensive laundry detergents which exhibit both good cleaning and sudsing characteristics.
The manufacture and use of synthetic laundry detergents containing mixtures of nonionic and anionic surfactants has been documented in the patent literature. See, for example, Bonaparte et al. U.S. Pat. No. 3,920,586 and Lengyel et al U.S. Pat. No. 4,464,292 (both of which are incorporated herein by reference in their entirety). Moreover, the use of ethoxylated alcohols (referred to herein, for convenience, by the xe2x80x9cEAxe2x80x9d acronym) as the nonionic constituent of such mixtures, and ethoxy sulfates (referred to herein by the xe2x80x9cESxe2x80x9d acronym) as the anionic constituent of such mixtures has also been described (see the aforesaid Bonaparte patent, column 2, lines 32-37; column 3, lines 17-28; column 9, lines 30-45; and column 9, line 67 column 10, line 20).
Dry blended laundry detergents containing such EA/ES or other nonionic/anionic surfactant systems are further described, for example, in Winston et al. U.S. Pat. No. 4,265,790 (incorporated herein by reference. In the past, however, when for cost purposes EA""s have been utilized as the nonionic constituent of such surfactant systems, the sudsing characteristics of the resulting dry blended detergent formulations have been impaired. Moreover, the use of EA/ES surfactant systems in dry blended detergent powders has been said to interfere with the processing characteristics thereof. Various efforts have been made to improve such processing characteristics. See, for example, Kowalchuk U.S. Pat. Nos. 4,137,197, and 4,162,994, both of which are incorporated herein by reference.
It has also been suggested in the patent literature that EA/ES mixtures useful in detergent compositions may be prepared by the direct sulfation of various EA materials. See, for example,
Roele U.S. Pat. No. 3,309,392, and Harris U.S. Pat. No. 3,959,186 (both incorporated herein by reference). The Roele patent describes a two-stage, gas phase reaction for the sulfation of EA""s having at least 8 carbon atoms with sulfur trioxide/inert gas mixtures. The final products, which are said to be useful as detergents, wetting agents or the like, are sulfated with conversions ranging from 87 to 97%.
The Harris patent, on the other hand, describes the sequential partial sulfation of, first, a highly ethoxylated EA (incorporating from 8 to 25 moles of ethoxylate per mole of the alcohol) and, thereafter, a less ethoxylated compound (incorporating from 2 to 12 moles of ethoxylate per mole of alcohol, but at least 4 ethoxylate groups per mole less than the EA first sulfated). Harris further discloses that, after neutralization of the partial sulfate mixture thus produced, the resulting product may contribute both detergent and builder properties to dry detergent formulations. Detergents incorporating the same are said to be capable of dispersing lime soap and to possess satisfactory washing characteristics as compared with other commercial dry powder detergents.
Lengyel et al, U.S. Pat. No. 4,464,292 discloses sulfation of (a) a blend of an alcohol and an alkyl ethoxylate or (b) a blend of an alkylaryl-OH (AAr) and an alkylarylethoxylate (AArE) and the use of the blend of the sulfated and unsulfated product which results in laundry detergents. While Lengyel mentions the degree of ethoxylation generally can be from 1-12 ethoxy units, only the alkyl ethoxylates are mentioned specifically with ethoxylations of less than 8 units. The only alkylaryl-O-ethoxylates mentioned have 8-10 ethylene oxide units per mole of alkylaryl-OH.
Although the art surfactant systems provide workable laundry detergent products, the laundry detergent area is a very cost conscious field and there are always efforts at developing lower cost alternatives that provide the same or better cleaning products. In addition, cost savings are also sought in manufacturing processes by eliminating steps or reducing energy demands, etc. meeting these goals takes on additional challenges when dealing with liquid formulations as components which might not interact when in a powder formulation may adversely interact in liquid formulations. Furthermore, liquid formulations may separate on storage, especially when subjected to extremes of temperature as may be encountered in the normal commercial distribution chain.
It is among the objects of the present invention to provide an improved process for the preparation of mixed AArE/AArES surfactants, which process may be efficiently and inexpensively carried out.
Another object of the invention is to provide a liquid laundry product which has improved stability while maintaining desired viscosity, performance, and soda ash loading.
A further object is to provide such surfactants, and detergents incorporating the same, which exhibit the detergency (cleaning) and esthetic (whiteness) characteristics required of commercial laundry detergents and which, moreover, have substantially improved sudsing characteristics.
It is a further object of the invention to provide a detergent which is more tolerant of high soda ash content, especially in liquid detergent formulations, than otherwise.
Yet another object of the invention is to provide a detergent formulation, especially a liquid detergent formulation, which has an increased soda ash content so as to permit a reduced surfactant content and thereby reduce overall detergent cost.
Still other objects of the invention will be recognized by those of ordinary skill in the art.
These objects are surprisingly achieved by the utilization of a mixture of alkylaryl-O-ethoxylates and the corresponding sulfates thereof as the surfactant portion of a high soda ash content laundry detergent, especially a high soda ash liquid laundry detergent. The mixture of alkylaryl-O-ethoxylates (which is then partially sulfated) is of the formula:
xe2x80x83C6-12alkyl-C6-10aryl-Oxe2x80x94(CH2CH2O)nOHxe2x80x83xe2x80x83(I)
where there is at least one component where n is 1-6 (the low ethoxylate component) and at least one component where n is 7-12 (the high ethoxylate component). This mixture is then partially sulfated generally in the manner shown by Lengyel (except that there is no free alkylaryl-OH). The at least 4 part mixture (of the low ethoxylate component, the high ethoxylate component, and their respective sulfates) is then used in amounts of up to about 50% of the formulation of a laundry detergent, especially a liquid laundry detergent.
Not Applicable
Ethoxylated aryl alcohols which are partially sulfated in the practice of this invention have the formula
C6-12alkyl-C6-10aryl-Oxe2x80x94(CH2CH2O)nOHxe2x80x83xe2x80x83(I).
The C6-12alkyl group is preferably selected from alkyl groups of 7-11 carbon atoms, more preferably 8-10 carbon atoms, and still more preferably is nonyl. It may be straight or branched, but straight chains are preferred. The C6-10aryl group is preferably phenyl or naphthyl, with phenyl being preferred. The number of ethoxy units (n) in the low ethoxy component is about 1 to about 6, preferably about 1.5 to about 5.5, more preferably about 2 to about 5, still more preferably about 3 to about 4, and most preferably about 4. The number of ethoxy units (n) in the high ethoxy component is about 7 to about 14, preferably about 8 to about 12, more preferably about 9 to about 10, and most preferably about 9. While the most preferable mixture to be used for partial sulfation in the present invention is a mixture where the low ethoxylate component has n=4 and the high ethoxylate component has n=9, other mixtures are suitable as well. Furthermore, while the most preferred mixture for sulfation in the instant invention has the C6-12alkyl group in the low and high ethoxylate components as the same, the present invention is not so limited, and the low ethoxylate component and the high ethoxylate component need not have the same C6-12alkyl group. Similarly, the points of attachment of the C6-12alkyl and the ethoxylated hydroxy on the C6-10aryl need not be the same in the low and high ethoxylate components, however, it is preferred if they are the same, and while any substitution arrangement of the aryl (such as o, m, or p when the C6-10aryl is phenyl) is acceptable, a para relationship is preferred between the C6-12alkyl group and the ethoxylated hydroxy (the analogous substitution patterns are preferred when the C6-10aryl is naphthyl). While preferable that there be no other substitutions on the C6-10aryl group, there is no requirement that there be none, and additional substitutions which do not negatively impact the ability to preferentially partially sulfate the free end of the ethoxy chain and do not materially adversely affect the detergency action of the component are acceptable.
Although the preferred blend which is subject to sulfation in the present invention is intended to be a binary mixture of one low ethoxylate component and one high ethoxylate component, it is recognized that in many instances, the xe2x80x9callegedly single chemical materialsxe2x80x9d are in actuality a mixture of materials having a relatively narrow range of ethoxy groups, with the major portion being the stated component. As such, the invention specifically includes those embodiments where there is more than one low ethoxylate component and/or more than one high ethoxylate component which mixture is then subjected to partial sulfation in the present invention. As used throughout the rest of this disclosure and claims, the term xe2x80x9cbinary mixturexe2x80x9d refers to a mixture in which there are two components which are either pure chemicals or in one or both of such components there is a single chemical which is the major constituent amongst a blend of homologs thereof.
The most preferred binary mixture which is subjected to the partial sulfation of the instant invention is a mixture of nonylphenol ethoxylate (4 mole) and nonylphenol ethoxylate (9 mole), the number of moles in parentheses referring to the number (on average) of ethoxy units per mole of compound. Most preferably the nonyl group is, relative to the ethoxylated hydroxy, in a 1,4-relationship (para arrangement) when the aryl is phenyl.
The ratio of the high ethoxylate component to low ethoxylate component may vary over wide ranges as desired, but is typically in a weight ratio of from 90:10 to 10:90, more preferably from about 85:15 to about 60:40, more preferably about 80:20 to about 65:35, still more preferably from about 75:25 to about 70:30, most preferably about 75:25 (high ethoxylate component:low ethoxylate component). In this context, xe2x80x9cthe high ethoxylate componentxe2x80x9d means the total of sulfated as well as unsulfated high ethoxylates and the xe2x80x9clow ethoxylate componentxe2x80x9d means the total of sulfated and unsulfated low ethoxylates.
The above blends that are to be subjected to sulfation in the present invention are then sulfated by reacting it with sulfuric acid, preferably concentrated sulfuric acid, most preferably at least 99% sulfuric acid, in a molar ratio of sulfric acid to alkylaryl-O-ethoxylate of about 0.2:1 to about 1.5:1, more preferably 0.5:1 to about 1.25:1, still more preferably about 0.75:1 to about 1.1:1, even more preferably about 0.9:1 to about 1:1, most preferably about 1:1. The resulting mixture (each ethoxylate component is partially sulfated to a mixture of unsulfated and sulfated forms of each ethoxylate constituent of the pre-reaction mixture) is then quenched with a suitable base, preferably sodium hydroxide to neutralize any remaining acid. (The pre-neutralized partially sulfated materials may be used directly as is if the detergent formulation will contain sufficient alkaline materials to neutralize the acids in the reaction mixture; however, it is generally best to neutralize the partially sulfated reaction product mixture before utilizing it for the final formulation of product from both a safety issue and sensitivity of other components of the final detergent formulation.) The neutralized result may then be used as is as the surfactant component of a laundry detergent in varying levels. (All of the following amounts are calculated on the basis of just the surfactant molecules and being exclusive of any water or sodium sulfate used or produced in the reaction.) The resulting partially sulfated mixture is used, based on the final laundry detergent product, in amounts of up to 50% of the laundry detergent, preferably in levels of from about 1% to about 45%, more preferably from about 2% to about 40%, still more preferably about 3% to about 30%, even more preferably from about 6% to about 25%, most preferably in amounts of about 6% to about 8%, about 10% to about 12%, about 15% to about 18%, about 20% to about 23%. Formulations wherein the surfactant component prepared above is used in amounts of about 6.5% to about 6.9% and about 21.9% and about 22.1%.
Alkylaryl-substituted EA""s such as the commercially available blends of nonyl phenol nominally ethoxylated with 1.5, 2, 3, 4, 5, or 6 moles of ethylene oxide per mole nonyl phenol (e.g. NP-1.5, 2, 3, 4, 5, and 6 respectively, available from Union Carbide or Huntsman), and the commercially available blends of nonyl phenol nominally ethoxylated with 8, 8.5, 9 or 10 moles of ethylene oxide per mole of nonyl phenol (e.g., NP-8, 8.5, 9 and 10, respectively, available from Union Carbide or Huntsman), may be partially sulfated in the present process.
It will be understood that the partial sulfation reaction may be carried out employing either batch or continuous operations. The specific reaction times and temperatures may be varied, depending upon the particular reaction system utilized and the specific degree of sulfation desired for any particular application. It will also be understood that, if desired, the sulfation reaction may be carried out employing oleum (20-30%), liquid or gaseous SO.sub.3, or chloro-sulfonic acid as the partial sulfating agent in lieu of concentrated sulfuric acid. The use of the latter material is, however, preferred since it obviates the necessity to employ special manufacturing equipment which may be necessary for the safe-handling and environmental control of fuming sulfuric acid or like reactants.
It is preferred to produce the sulfated/unsulfated blend by partial sulfation followed by neutralization as described more fully hereinabove. Alternatively, it is within the purview of the present invention to form the sulfated/unsulfated surfactant blends utilized herein by mixing the unsulfated components with their fully sulfated respective counterparts (with neutralization being conducted either before or after mixing.
Employing the partial sulfation technique, following sulfation the reaction mixture is neutralized in conventional manner with any desired base, e.g., with sodium hydroxide, soda ash, or other desired alkali metal or ammonium hydroxide or carbonate. Preferably, when the neutralized partially sulfated reaction mixture is to be utilized as the surfactant system in a dry powder detergent, the neutralization is effected simultaneously with dry blending of the surfactant with the further ingredients of the detergent formulation. Alternatively, the reaction mixture may be separately neutralized with an appropriate base, and the neutralized material thereafter blended with the further detergent ingredients.
Detergent formulations typically additionally contain one or more builder salts or compounds, alkali metal silicate corrosion inhibitors, and one or more further adjuvants such as pH buffering compounds, soil suspending agents, oxidizing agents, enzymes, optical brighteners, fillers, perfumes, coloring agents, or oleic acid for suds control and/or viscosity modification, or the like.
The builder salts, which peptize soil and remove water hardness ions, include various inorganic phosphates, pyrophosphates, borates, carbonates, bicarbonates, sesquicarbonates, silicates and zeolites, and organic compounds including citrates, EDTA (such as VERSENE available from Dow), NTA or alkanolamines. Various organic amines may also be incorporated as suds builders, including alkanolamides, amine oxides and alkanolamines. The soil suspending agents include colloids such as carboxymethylcellulose, polyvinyl alcohol, polymers such as polymer 445 (a polyarylate homopolymer having a molecular weight of about 3000 to about 8000, more specifically about 4000 to about 5000) or the like. Oxidizing agents which may be incorporated in such formulations for stain removal include the alkali metal perborates and percarbonates; enzymes such as the alkalases, proteases or the like can be added for similar purposes. Optical brighteners such as UNPA from Ciba (Stilbene chemistry Florescent whitening agents) more specifically a cyanuric chloride/diamino stilbene disulfonic acid compound. Dyes and fragrance are further optional ingredients.
Those skilled in the art will recognize that any of the preceding or various other recognized detergent ingredients may be blended with the surfactants of this invention to provide useful dry blended detergent formulations. Such further ingredients are further disclosed, for example, in the aforesaid Winston et al. application, the pertinent disclosure of which is incorporated by this reference herein.
The liquid formulations may additionally include sequestrants, viscosity modifiers, and any of the various adjuvants noted hereinabove. Typical constituents of liquid detergent formulations which may be thus admixed with the surfactants of the present invention are disclosed, for example, in Collins U.S. Pat. No. 3,869,399, the disclosure of which is additionally incorporated by this reference herein.
One of the primary advantages of the formulation of the instant invention is that while maintaining desired viscosity, performance and stability in a liquid laundry detergent product, the partially sulfated mixture of the invention is much more tolerant of soda ash than the same formulation having a partially sulfated composition of only one average ethoxylate of the alkylaryl-O-ethoxylate. In other words, a formulation with a low-ethoxylate and a high ethoxylate (each partially sulfated) is more tolerant of soda ash and the formulation is more stable than the same formulation with only a low ethoxylate (partially sulfated) or the same formulation with only a high ethoxylate (partially sulfated). This greater tolerance of soda ash means that the liquid laundry formulation of the invention can contain a greater amount of soda ash and as such the amount of the surfactants can be reduced. Since soda ash is much less expensive than the surfactants, this results in an overall lower cost for the final product per unit of use.